In the past commercial needs for urethanes were satisfied, at least in part, by reacting an isocyanate with a compound containing a hydroxyl group under elevated temperature conditions. Expense of the isocyanate starting compounds and toxicity problems have caused new methods to be sought for the commercial production of urethanes.
U.S. Pat. 3,338,956 and 3,448,140 for example, have proposed that the manufacture of urethanes be accomplished by reacting an organic compound containing at least one hydroxyl group with carbon monoxide and a nitrogenous compound under superatmospheric pressure and elevated temperature conditions in the presence of a catalyst such as Cr, Mo, W, Mn, Fe, Co, Ni, Ru, Rh, Os and Ir compounds. Although the processes described by these patents employ low cost nitrogenous compounds as starting materials, various factors, including relatively low product yields, long reaction times and high pressure have kept the processes from being economical for obtaining urethanes of high purity on a commercial basis. Among the problems involved with these prior art processes is the fact that many of the suggested catalysts are expensive and difficult to separate from the desired urethane products. Unless the catalyst can be separated for reuse, catalyst loss generally tends to make the expense of using the process prohibitive for commercial purposes. Furthermore, the absence of catalyst separation results in metal contamination of the urethane products.